<s>
SCSI	B-Application
Enclosure	I-Application
Services	I-Application
(	O
SES	O
)	O
is	O
a	O
protocol	O
for	O
more	O
modern	O
SCSI	B-Architecture
enclosure	B-Device
products	O
.	O
</s>
<s>
An	O
initiator	B-Device
can	O
communicate	O
with	O
the	O
enclosure	B-Device
using	O
a	O
specialized	O
set	O
of	O
SCSI	B-Architecture
commands	O
to	O
access	O
power	O
,	O
cooling	O
,	O
and	O
other	O
non-data	O
characteristics	O
.	O
</s>
<s>
Attached	B-Application
enclosure	I-Application
services	I-Application
devices	O
allow	O
SES	O
communication	O
through	O
a	O
logical	O
unit	O
within	O
one	O
SCSI	B-Architecture
disk	O
drive	O
located	O
in	O
the	O
enclosure	B-Device
.	O
</s>
<s>
The	O
disk-drive	O
then	O
communicates	O
with	O
the	O
enclosure	B-Device
by	O
some	O
other	O
method	O
,	O
the	O
only	O
commonly	O
used	O
one	O
being	O
Enclosure	B-Device
Services	O
Interface	O
(	O
ESI	O
)	O
.	O
</s>
<s>
Standalone	O
enclosure	B-Device
services	O
enclosures	O
have	O
a	O
separate	O
SES	O
processor	O
which	O
occupies	O
its	O
own	O
address	O
on	O
the	O
SCSI	B-Architecture
bus	O
.	O
</s>
<s>
The	O
protocol	O
for	O
this	O
uses	O
direct	O
SCSI	B-Architecture
commands	O
.	O
</s>
<s>
An	O
enclosure	B-Device
can	O
be	O
fault-tolerant	O
by	O
containing	O
two	O
SES	O
processors	O
.	O
</s>
<s>
The	O
SCSI	B-Device
initiator	I-Device
communicates	O
with	O
an	O
SES	O
device	O
using	O
two	O
SCSI	B-Architecture
commands	O
:	O
Send	O
Diagnostic	O
and	O
Receive	O
Diagnostic	O
Results	O
.	O
</s>
<s>
Some	O
universal	O
SCSI	B-Architecture
commands	O
such	O
as	O
Inquiry	O
are	O
also	O
used	O
with	O
standalone	O
enclosure	B-Device
services	O
to	O
perform	O
basic	O
functions	O
such	O
as	O
initial	O
discovery	O
of	O
the	O
devices	O
.	O
</s>
<s>
The	O
SCSI	B-Architecture
Send	O
Diagnostic	O
and	O
Receive	O
Diagnostic	O
Results	O
commands	O
can	O
be	O
addressed	O
to	O
a	O
specific	O
SES	O
element	O
in	O
the	O
enclosure	B-Device
.	O
</s>
<s>
The	O
SCSI	B-Architecture
command	O
protocols	O
assume	O
that	O
there	O
may	O
be	O
more	O
than	O
one	O
of	O
each	O
device	O
type	O
so	O
they	O
must	O
be	O
each	O
given	O
an	O
8-bit	O
address	O
.	O
</s>
<s>
This	O
allows	O
an	O
enclosure	B-Device
to	O
detect	O
and	O
report	O
unacceptable	O
environmental	O
conditions	O
.	O
</s>
<s>
The	O
SCSI	B-Architecture
standard	O
allows	O
for	O
two	O
different	O
threshold	O
levels	O
,	O
noncritical	O
(	O
warning	O
)	O
and	O
critical	O
.	O
</s>
<s>
A	O
larger	O
SCSI	B-Architecture
storage	O
enclosure	B-Device
may	O
contain	O
multiple	O
subenclosures	O
.	O
</s>
<s>
SCSI	B-Application
attached	I-Application
enclosure	I-Application
services	I-Application
is	O
a	O
computer	O
protocol	O
used	O
mainly	O
with	O
disk	O
storage	O
enclosures	O
.	O
</s>
<s>
It	O
allows	O
a	O
host	O
computer	O
to	O
communicate	O
with	O
the	O
enclosure	B-Device
to	O
access	O
its	O
power	O
,	O
cooling	O
,	O
and	O
other	O
non-data	O
characteristics	O
.	O
</s>
<s>
The	O
host	O
computer	O
communicates	O
with	O
the	O
disks	O
in	O
the	O
enclosure	B-Device
via	O
a	O
SCSI	B-Architecture
interface	O
which	O
may	O
be	O
Parallel	O
SCSI	B-Architecture
,	O
FC-AL	B-Architecture
,	O
SAS	O
,	O
or	O
SSA	B-Architecture
.	O
</s>
<s>
One	O
of	O
the	O
disk	O
devices	O
located	O
in	O
the	O
enclosure	B-Device
is	O
set	O
up	O
to	O
allow	O
SCSI	B-Application
Enclosure	I-Application
Services	I-Application
(	O
SES	O
)	O
communication	O
through	O
a	O
logical	O
unit	O
.	O
</s>
<s>
The	O
disk-drive	O
then	O
communicates	O
with	O
the	O
SES	O
processor	O
in	O
the	O
enclosure	B-Device
,	O
usually	O
via	O
Enclosure	B-Device
Services	O
Interface	O
(	O
ESI	O
)	O
,	O
or	O
a	O
protocol	O
called	O
DSI	O
for	O
SSA	B-Architecture
enclosures	O
.	O
</s>
<s>
The	O
data	O
sent	O
over	O
the	O
ESI	O
or	O
DSI	O
interface	O
is	O
simply	O
the	O
contents	O
of	O
a	O
SCSI	B-Architecture
command	O
and	O
the	O
response	O
to	O
that	O
command	O
.	O
</s>
<s>
Only	O
two	O
SCSI	B-Architecture
commands	O
are	O
implemented	O
by	O
attached	B-Application
enclosure	I-Application
services	I-Application
devices	O
:	O
</s>
